It's funny when people make plans on the actions of others. I have learned my lesson the hard way a few times that I now find it ridiculous. Human beings are both fragile and unpredictable. As much as a certain level of trust is needed to operate, it is almost naive to see a case of absolute reliance on another person.
It is especially true when we are incentivized to be selfish. Let's face it, in today's World we are certainly incentivized to act solely on our own behalf in a lot of things. It's a me-centric World and no surprises that people are a lot more selfish. Even those who seemingly take actions on behalf of others have more selfish intentions hidden in their actions.
It probably should be the norm to expect that people act in their own self interests but it sometimes isn't. We tend to be naive and get carried away by sweet words or intentions rather than actual actions on display. It often takes painful and bitter experiences to finally make this switch and begin to uphold people to the actions they portray rather than what they say. Most times it is too late by the time it gets to this stage.
When dealing with people my philosophy is usually to take nothing at face value. This includes my workplace, social life and politics. The only exception to this is family because even if they fall short of expectations, I would rather be at liberty to place my trust in them.